Yellowstone Grizzlies May Soon Commingle With Northern Cousins

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A grizzly bear in Yellowstone National Park. Biologists say that as grizzly populations increase, more male bears are venturing farther from park boundaries, sometimes to locations where they have not been seen in a century or more.CreditGeorge Sanker/NPL, via Minden Pictures

HELENA, Mont. — To make the plains and mountains safe for the great herds of cattle that were brought to the West at the end of the 19th century, grizzly bears were routinely shot as predators by bounty hunters and ranchers.

Ever since, the bears in Yellowstone National Park, protected from hunting, have been cut off from the rest of their kind. Their closest kin prowl the mountains some 70 miles north, in and around Glacier National Park.

In a new paper, biologists say that as grizzly populations increase in both Glacier and Yellowstone, more adventurous males from both parks are journeying farther to stake out territory, winding up in places where they have not been seen in a century or more.

If they keep roaming and expanding, the two populations will likely reconnect, perhaps as soon as five or 10 years from now.

“It’s very encouraging for the long-term future of the bear,” said Frank van Manen, leader of the Interagency Grizzly Bear Study Team in Bozeman, Mont., which oversees research into Yellowstone’s bears.

A mingling of the separate populations would go a long way toward bolstering the genetics of the isolated Yellowstone grizzlies.

The bears in the Greater Yellowstone ecosystem, in and around the park, are healthy now, and they have increased to at least 700 today from fewer than 150 in 1975, when they were listed as endangered.

But a genetic lifeline from Glacier bears, which are also related to the grizzlies of Canada, will mean a good deal more diversity to help assure the bears’ future. It’s so important that researchers have talked about trucking grizzly bears from the north to add to the Yellowstone gene pool.

“Because Yellowstone is a bit lower in genetic diversity, hundreds of years from now they might be less able to adapt to changing conditions — changing climate, changing food sources and disease resistance,” Dr. van Manen said.

While no one knows what advantageous traits the Glacier grizzlies might have in their genes, increasing diversity is the best way to assure resilience against those types of hazards.

Currently, the nearest interloper from the Northern Continental Divide Ecosystem has bridged the 70-mile gap by working his way south. That grizzly is in the mountains near Butte, Mont., some 50 miles from the perimeter of the Yellowstone ecosystem.

Biologists and conservationists are rooting for a natural reunion between the two largest populations of grizzlies in the country, Dr. van Manen said.

A grizzly on a road near Mammoth, Wyo. Scientists say if bears keep roaming from Yellowstone and Glacier National Park, the two populations will likely reconnect.CreditDavid Grubs/The Billings Gazette, via Associated Press

The effort to follow these nomadic bears was aided by satellite data collars and new, more powerful data analysis techniques. Some 124 males were monitored from 2000 to 2015, some for more than one year.

GPS collars can track a bear almost in real time, providing richly detailed information on the corridors and habitats they use that need to be protected.

While much of the land between the two parks is publicly owned and wild, it becomes a gauntlet in some places as bears migrate into towns, cities, ranches and farms.

The bears are likely to seek out dog food, beehives, garbage, chickens and even apple trees, getting into trouble that may require trapping and relocating them. Highway crossings, especially on I-90 and I-15, pose a serious risk.

Conservation groups and biologists say it’s a race against time to protect some of the open land between the two parks and to assure permanent transit routes for wildlife through land purchases or conservation easement.

Residential housing development north of Yellowstone around Bozeman, for example, is soaring.

“Even one house per square mile can be a problem for bears,” said Jodi Hilty, a wildlife biologist in Canmore, Canada. “At the same time, this is one of the most intact mountain ecosystems in the world.”

Dr. Hilty heads the group Yellowstone to Yukon, which seeks to link bears and other Yellowstone wildlife with populations in Glacier National Park and in vast tracts of wilderness in Canada. Protecting migration corridors between Yellowstone, Glacier and Canada would benefit not just bears, she said, but cougars, wolverines and other animals.

The Fish and Wildlife Service has removed the protections afforded under the Endangered Species Act from the Yellowstone grizzly because the population has grown so large. Dr. van Manen said that the number of grizzlies may exceed 1,000.

Environmentalists have sued the agency over its decision. They argue that climate change is a wild card that might someday cause the Yellowstone bear population to collapse.

With the bears delisted, some are concerned about plans by Montana officials to allow the hunting of Yellowstone grizzlies. Dr. David Mattson, a retired wildlife biologist, said that there is a good chance that “Montana will institute a more lethal regime, whether by sport hunting or by other means, that will compromise these prospects.”

The state has said it would not allow hunting in areas where the two populations might reconnect.

As bears explore far beyond their core habitats, people not accustomed to grizzlies need to be educated about bear-proofing garbage cans and sealing off beehives and chicken coops with electric fencing, Dr. van Manen said.

Carrying pepper spray has already become indispensable for hikers, hunters and others in many parts of Montana, Idaho and Wyoming.

In 2016, four grizzlies were killed after confronting hunters in “defense of life” scenarios. Recently, a game warden near Cody, Wyo., shot and killed a female grizzly when it charged at him, leaving her cubs orphans.

Generally, though, the news for the big bear is good, said Dr. van Manen.

“There is strong scientific evidence that the recovery process that was put into place starting in the mid 1970s has paid off,” he said. “It’s an extraordinary effort for recovery of a species that has ability to kill people. For the American people to support it is a remarkable achievement.”